Selecting the Correct pH for Vehicle Cleaning
Acids are generally used to clean inorganic compounds (like oxide scale, metal deposits, water scale etc.), while bases are generally used to clean organic compounds (greases, oils, insects, sap, resin, fats, proteins etc.).
Dirt and grime from the road is predominantly a mixture of organic compounds, hence alkaline detergents are usually better suited for cleaning the exterior of the vehicle. Acidic detergents are best suited for areas which accumulate oxide scale (rust), metal deposits and water scale, for example, the underside of the vehicle, inside wheel arches and on the wheels themselves.
Important notes:
- Highly acid detergents should only be used on painted or powder-coated rims for a deep but infrequent clean. Care should be taken if the paint or powder-coating is damaged, exposing the raw alloy. Do not use on anodised, chrome-coated or diamond cut rims. Do not use on hot surfaces. Care should be taken to avoid contact with painted body work or glass. Dwell times should not be exceeded and a base used to neutralise the acid if unable to rinse the area thoroughly. "Fallout removers" which have a more neutral pH are better suited for on-going cleaning.
- Neutral alkalis are preferred for cleaning upholstery. Use mild alkalis where upholstery is heavily soiled.
- Strong acids and alkalis can adversely affect dyes and damage fibres.
- Close-to-neutral pH is required when cleaning wool, silk or any fibre marketed as stain-resistant.
- Protein fibres (like wool and silk) can tolerate a limited amount of mild acid, and cellulose can tolerate a certain degree of alkalinity; however, both can be destroyed by strong acids or alkalis.
- Olefin fibres, found in some carpets, can withstand high alkalinity.
- Solution dyed nylon, polyester and acrylic fibres can withstand moderate alkalinity.
| Cleaner Type | pH Range | Substance to Remove |
|---|---|---|
| Mineral-acid | 0.0–2.0 | Heavy oxide scale (e.g. rust) |
| Mild acid | 2.0–5.5 | Inorganic salts (e.g. lime-scale on windows), water soluble metal complexes (e.g. brake-pad deposits) |
| Neutral | 5.5–8.5 | Light oils and small particles like dust |
| Mild alkaline | 8.5–11.0 | Oils, particulates, films |
| Alkaline | 11.0–12.5 | Oils, fats, proteins, insects, resin, sap, tar |
| Highly alkaline | 12.5–14.0 | Heavy grease/oils |